package com.byxy.computer.student.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 提供一系列获取和校验MD5的方法
 */
public class MD5Util {

	/**
	 * 获取该输入流的MD5值
	 * 
	 * @param is
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static String getMD5(InputStream is) throws NoSuchAlgorithmException, IOException {
		StringBuffer md5 = new StringBuffer();
		MessageDigest md = MessageDigest.getInstance("MD5");
		byte[] dataBytes = new byte[1024];

		int nread = 0;
		while ((nread = is.read(dataBytes)) != -1) {
			md.update(dataBytes, 0, nread);
		}
		;
		byte[] mdbytes = md.digest();

		// convert the byte to hex format
		for (int i = 0; i < mdbytes.length; i++) {
			md5.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
		}
		return md5.toString();
	}

	/**
	 * 获取该文件的MD5值
	 * 
	 * @param file
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static String getMD5(File file) throws NoSuchAlgorithmException, IOException {
		FileInputStream fis = new FileInputStream(file);
		return getMD5(fis);
	}

	/**
	 * 获取指定路径文件的MD5值
	 * 
	 * @param path
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static String getMD5(String path) throws NoSuchAlgorithmException, IOException {
		FileInputStream fis = new FileInputStream(path);
		return getMD5(fis);
	}

	/**
	 * 校验该输入流的MD5值
	 * 
	 * @param is
	 * @param toBeCheckSum
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static boolean md5CheckSum(InputStream is, String toBeCheckSum)
			throws NoSuchAlgorithmException, IOException {
		return getMD5(is).equals(toBeCheckSum);
	}

	/**
	 * 校验该文件的MD5值
	 * 
	 * @param file
	 * @param toBeCheckSum
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static boolean md5CheckSum(File file, String toBeCheckSum) throws NoSuchAlgorithmException, IOException {
		return getMD5(file).equals(toBeCheckSum);
	}

	/**
	 * 校验指定路径文件的MD5值
	 * 
	 * @param path
	 * @param toBeCheckSum
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static boolean md5CheckSum(String path, String toBeCheckSum) throws NoSuchAlgorithmException, IOException {
		return getMD5(path).equals(toBeCheckSum);
	}
}